Automatic choke for small carburetors



April 11, 1961 E. L. RAPPLEAN ETAL AUTOMATIC CHOKE FOR SMALL CARBURETORSFiled July 8, 1957 Wan @IIIIA MARTIN 2 Sheets-Sheet 1 INVENTORS EUGENEL. RAPPLEAN WENFORD E.HIGHLEY E. FUCHS elland/ M ATTORNEY A ril 11, 1961E. L. RAPPLEAN ETAL 2,979,047

AUTOMATIC CHOKE FOR SMALL CARBURETORS 2 Sheets-Sheet 2 Filed July 8,1957 FlG.6

INVENTORS EUGENE L. RAPPLEAN WENFORD E. HIGHLEY MARTIN E. FUCHS u wf/mwdATTORNEY re tates 2,979,047 AUTOMATIC CHOKE FOR SMALL CARBURETORS FiledJuly 8, 1957, Ser. No. 67%,452 6 Claims. (Cl. 123-119) This inventionrelates to carburetors of the type employed for supplying a fuel-airmixture to small two or four cycle internal combustion engines, and ismore particularly, concerned with automatic choke contiol devices forsmall carburetors.

In the operation of small internal combustion engines, carburetor chokevalves are usually provided with manual control means, whereby the chokevalve may be closed to enrich the fuel mixture to facilitate starting ofthe engine. After starting of the engine, the choke valve is manuallyopened to lean out the fuel mixture. As engine driven devices are nowcommonly operated by those unskilled in carburetion, it is an object ofthe invention to provide an automatic choke control means particularlyadapted for use in starting small engines.

Another object of the invention is to provide an automatic choke controldevice embodying a temperature responsive means and a suction responsivemeans coacting to regulate the position of the choke valve duringstartmg and running of an engine to provide the proper fuela1r mixture.

A further object of the invention is to provide an automatic chokecontrol device adapted to prevent immediate complete closing of thechoke valve when the engine is stopped to thus provide a leaner mixturefor restarting of the engine when it is hot.

Another object of the invention resides in the provision of an automaticchoke control device in which the operation of the suction responsivemeans is controlled by a thermostatically controlled air bleed valve.

Another object of the invention is to provide a device operableresponsive to intake manifold suction for opening the choke valve, andmeans for dampening manifold pulsations to prevent fluttering of thechoke valve.

Another object is to provide an automatic choke control which isrelatively simple, inexpensive to manufacture, and reliable in use.

The invention embodies other novel features, details of construction,and arrangement of parts which are hereinafter set forth in thespecification and claims, and illustrated in the accompanying drawings,wherein:

Fig. l is an elevation, partly in section, illustrating a carburetorchoke control embodying features of the in-' vention, the choke valvebeing shown in its closed position for starting a cold engine.

Fig. 2 is an elevation, corresponding to Fig. 1, showing the choke valvein its slightly open position for restarting a heated engine. I

Fig. 3 is a fragmentary elevation showing parts of the controlstructure.

Fig. 4 is a sectional view showing a thermostatically controlled airbleed valve structure.

5, 6, and 7 are elevationsillustrating a modified form of the invention.

Referring now to the drawings for a better understanding of theinvention and, more particularly, to Figs. 1 to 4, therein, theautomatic choke control is shown as applied to a small carburetorcomprising a body 6 having r 2,979,047 Patented Apr. 11, 1961 a mixtureconduit 7 provided with an inlet 8, outlet 9, and a venturi 11. A chokevalve 12 is disposed within the inlet 8 and fixed on a shaft 13journaled at its ends in the body 6 in a manner to be opened by enginesuction. A throttle valve 14 is disposed within the outlet 9 and fixedon a shaft journaled at its ends in the body 6.

The body 6 is formed with an annular recess 16 to receive the rim of aconstant level fuel bowl 17 which is secured to a tubular boss 18 on thebody by means of a screw 19. A float 21 is pivotally mounted within thebowl to actuate a conventional fuel inlet needle valve (not shown). Amain fuel nozzle 22-is threaded into the tubular boss 18 and formed witha fuel metering orifice 23 to receive the tapered end of a hollowmetering rod 24.

The metering rod 24 extends upwardly through the main fuel nozzle 22 andacross the mixture conduit 7 for engagement at its end with anadjustment screw 26 threaded-into the body 6. A fuel passage 27 isprovided in the boss 18 for the flow of fuel from the bowl upwardlythrough the orifice 23 and main fuel nozzle 22 into the mixture conduit7. An air bleed passage 28 leads from the inlet 8 into the annular space29 between the boss 18 and main fuel nozzle 22, the nozzle having airbleed apertures 31.

Fuel for idling operation of the engine passes intothe hollow meteringrod 24 through apertures 32, and thence outwardly through openings 33 inthe adjustment screw 26 into an idle passage 34 to an idle port 36 fordischarge into the mixture conduit 7 adjacent the edge of the throttlevalve 14 when the latter is disposed in idling position. Idle air bleedapertures 37 are provided in the metering rod 24.

In Figs. 1 and 2 in the drawings, the automatic choke control is shownas comprising a lever 38 fixed on the choke shaft 13 and provided with aslot 39 to receive an offset end 40 on the upper end of a link 42. Aninturned lug 4-3 is formed on the lever 38 for engagement by one end ofa bimetallic strip 41 which has its other end secured to the olfset end40 of the link 42. If desired, the medial portion of the strip 41 mayextend around the shaft 13.

The lower end of the link 42 is pivotally connected to the upper end ofa rod 44 secured to and actuated by a diaphragm 46 of a suction motor47. The marginal portion of the diaphragm is clamped between upper andlower housing sections 48 and 49, respectively, by means of cap screws51. The upper section of the motor 47 is secured to a bracket 52 by anut 53, and the bracket is secured to the body 6 by cap screws 54. Acompression spring 56 is seated on the lower housing section 49, withina suction chamber 57, to engage and yieldably resist downward movementof the diaphragm.

The lower housing section 49 is provided with an inlet nozzle 58 havingan upwardly seating check valve 59 therein for the purpose of dampeningpulsations of the diaphragm during operation of the engine, the checkvalve seat being scored to provide a slow leak of air past the valveinto the suction chamber 57 when the engine stops operating to cause thespring 56 to close the choke valve.

A conduit 61 leads from the nozzle 58 to one end of a suction passage 62in a thermostatically controlled air bleed device 63, the other end ofthe passage being connected to an engine intake manifold 64 by a conduit66. The device 63 ismounted on an engine exhaust manifold 67 andprovided with a bimetallic strip 68 pivotally mounted intermediate itsends on a pin 69. One end of the strip 68 engages an adjustment screw71, and theother end of the strip is adapted to engage a valve member 72to open a port in an air bleed passage 73 leading from atmosphere to thesuction passage 62. A spring 74 is provided to yieldably resist openingmovement of the valve member 72.

When the engine is not operating, the thermostat 41 will cool, rotatingthe choke lever 38 and valve 12 in a counter-clockwise direction towardclosed position as far as permitted by the engagement of the end of slot39 with the offset end 40 of link 42, which will be moved to its extremeposition in one direction by spring 56 acting on plunger 44. Bleedvalve72 will be held open by flexed thermostat 68, so that insufficientsuction will be applied to diaphragm 46 during cranking to affect thechoke position. When the engine starts direct action of air flow on theunbalanced choke, itself, will cause partial opening of the choke. Aslong as the valve 72 remains open, engine suction has no effect upon theposition of diaphragm 46 and plunger 44, so that the choke valve 12 andlever 38 are limited to a movement corresponding to the axonate lengthof slot 39. The left end of slot 39 engaging the end of link 40 limitschoke valve opening. 7

As the engine becomes heated, thermostat 68 will straighten, permittingclosure of bleed valve 72, and, ultimately, the effect of increasingmanifold suction applied to the diaphragm will cause correspondingmovement of plunger 44 and rod 42 as spring 56 is compressed.Concurrently, choke thermostat 41 will expand to shift lever 38 and thechoke valve relative to link 42, as in Fig. 2, but, of course, the valvecannot open faster than the end I 40 of rod 42 permits.

spring 76 are provided to move the choke valve 12 betweenits closed andpartly open position, as illustrated in Figs. ,5 and 6, respectively.The torsion spring 76 is connected at one end thereof to the choke shaft13 and at its other end to the body 6 to yieldably resist openingmovement of the choke valve 12.

The thermostat 41a has its inner end connected to the choke shaft 13,and its outer end in abutting engagement with an adjustment screw 77threaded through a boss 78 on the body 6. The thermostat 41a acts toprevent complete closing of the choke valve 12 upon stopping of a heatedengine to provide a proper fuel-air mixture for restarting of the enginein a heated condition. When a cold engine is not operating, the openingforce exerted by the torsion spring is overcome, and the thermostatholds the choke valve in closed position. This form of the invention isotherwise similar to the form heretofore shown and described.

Certain structures have been described herein which will fulfill all theobjects of the present invention, but it is contemplated that othermodifications will be obvious to those skilled in the art which comewithin the scope of the invention as defined by the appended claims.

We claim:

1. In a carburetion system for an internalcombustion engine, a chokevalve, suction means including a diaphragm motor responsive to manifoldsuction for opening and closing said choke responsive to starting andstopping of the engine, heat responsive means interposed between saidsuction means and choke valve to resistfull closing movement of saidchoke valve upon stopping of the engine to providea leaner fuel mixturefor restarting of the engine in a heated condition, and means forvarying the suction applied to said motor responsive to variations intemperature of the engine.

2. In a carburetion system for an internal combustion 4 engine, acarburetor body having a. mixture conduit, a choke shaft journaled insaid body, a choke valve fixed on said shaft, a lever fixed on saidshaft, suction responsive means having a lost-motion connection withsaid lever tending to open and close said choke valve, and temperatureresponsive means interconnecting said lever and said suction responsivemeans for varying the position of said lever relative to said suctionresponsive means, whereby said choke valve is biased to a slightly openposition to provide a leaner fuel mixture for restarting a heatedenglue.

3. In a carburetion system for an internal combustion engine, acarburetor body having a mixture conduit, a

choke shaft journaled in said body, a choke valve fixed on said shaft, alever fixed on said shaft, suction responsive means having a lost-motionconnection with said lever for opening and closing said choke valve, andtemperature responsive means for varying the position of said leverrelative to said suction responsive means, whereby said choke valve isheld in slightly open position to provide a leaner fuel mixture forrestarting a heated engine, said suction responsive means having a linkslidably engaged in a slot in said lever whereby said choke valve ismovable between closed and slightly open position responsive tomovements of said temperature responsive means.

4. In a carburetion stystem for an internal combustion engine, acarburetor body having a mixture conduit, a choke shaft journaled insaid body, a choke valve fixed on said shaft, a lever fixed on saidshaft, suction responsive means having a lost-motion connection withsaid lever for opening and closing said choke valve, temperatureresponsive means for varying the position of said lever relative to saidsuction responsive means, whereby said choke valve is held in slightlyopen position to provide a leaner fuel mixture for restarting a heatedengine, and means responsive to variations in temperature of the enginefor varying the suction force applied to said suction responsive means.

5. In a carburetion system for an internal combustion engine, acarburetor body having a mixture conduit, a choke shaft journaled insaid body, a choke valve fixed on said shaft, a lever fixed on saidshaft, suction responsive means having a lost-motion connection withsaid lever for opening and closing said choke valve, temperatureresponsive means for varying the position of said lever relative to saidsuction responsive means, whereby said choke valve is held in slightlyopen position to provide a leaner fuel mixture for restarting a heatedengine, and means including a thermostatically controlled air-bleedvalve structure responsive to variations in temperature of the enginefor varying thesuction force applied to said suction responsive means.

6. In a carburetion system for internal combustion engines, a chokevalve, suction means to open said choke valve, spring means to closesaid choke valve, means responsive to variations in engine temperaturefor moving said choke valve between closed and slightly open positions,and other means responsive to variations in engine temperature forvarying the force exerted by said suction means.

References Cited in the file of this patent UNITED STATES PATENTS2,030,331 Smith Feb. 11, 1936 2,222,865 Chandler Nov. 26, 1940 2,309,419Sisson Ian. 26, 1943 2,361,132 Smith Oct. 24, 1944 2,362,346 Blake Nov.7, 1944 2,403,720 Hunt July 9, 1946 2,408,349 Stanton Sept. 24, 19462,421,733 Henning June 3, 1947

